1. Field of the Invention
The present invention relates to a semiconductor wafer evaluating method for obtaining semiconductor devices having reliable gate oxide film, a semiconductor device manufacturing method for manufacturing semiconductor devices by using semiconductor wafers evaluated by the evaluating method.
2. Description of the Background Art
With the miniaturization and the increase in formation area of the semiconductor integrated circuits, improvements in reliability of the gate oxide film in MOS devices are becoming increasingly important. The reliability of the gate oxide film depends on the quality of the semiconductor wafer on which the gate oxide film is formed. Accordingly, obtaining a semiconductor device having highly reliable gate oxide film requires prior evaluation of the semiconductor wafer in manufacturing.
The following have been considered to be the main factors which affect the reliability of the gate oxide film:
(1) Quality of silicon crystal based on oxygen concentration in the silicon crystal; PA1 (2) Quality of silicon crystal based on crystal defects caused by heat history in the single-crystal growth; and PA1 (3) Quality of silicon crystal based on behavior of crystal defects caused by heat treatment before formation of the gate oxide film. PA1 (4) Quality of silicon crystal based on process defects caused in processes including the mirror polishing. PA1 (1) Forming the test pattern on a sample wafer requires a long turn-around time from the start of evaluation to the evaluation of the semiconductor wafers; PA1 (2) It requires process equipment for forming the test pattern; and PA1 (3) It requires a device for evaluating the dielectric breakdown characteristic.
Recently, with the use of lower temperatures in the semiconductor manufacturing processes, the following is also considered as a factor which affects the reliability of the gate oxide film, as well as the factors (1) to (3) above:
Evaluation of semiconductor wafers is described in Japanese Patent Laying-Open No.4-212433 and Japanese Patent Laying-Open No.7-206591, for example. These two references describe the crystal defects in the substrate surface as a cause, attributed to the semiconductor wafer, of the reduction in yield of devices formed on the semiconductor wafer, but neither of the two describes the factor (4) shown above.
For the purpose of obtaining a semiconductor device having highly reliable gate oxide film, a conventional evaluation of semiconductor wafers in manufacturing semiconductor devices is conducted by using actually formed gate oxide film. That is to say, a test pattern of the MOS structure having gate oxide film is actually formed on a mirror-polished object semiconductor wafer by applying processing such as oxidization, patterning, formation of interconnections, etc. with process apparatus. Next, the dielectric breakdown characteristic of the oxide film is measured with the test pattern by using a device (e.g., a tester) for measuring the dielectric breakdown characteristic (e.g., the TDDB (Time Dependent Dielectric Breakdown) characteristic). Next, the semiconductor wafer is evaluated from the measurements.
The above-described semiconductor wafer evaluation in fabrication of semiconductor devices, however, has the following problems: